An extremely facile and efficient procedure which has been developed for the synthesis of dihydropyrrol-2-ones. One-pot four-component reaction of amines, dialkyl acetylenedicarboxylates and formaldehyde in the presence of N,N,N,N-tetramethylguanidinium acetate [TMG][Ac] in methanol at ambient temperature provides substituted dihydropyrrol-2-ones in good to high yields. The important aspects of this multi-component heteroannulation are simple operations under mild conditions, readily available starting material and catalyst. Furthermore, All products were obtained through a simple filtration and washed with ethanol and no need for column chromatography. It is found that the catalyst is recyclable and can be used up to four times without significant loss of its activity.